It has been well known in the art to provide a rotary atomizing head on paint coating machines of the sort as mentioned above. Generally, in rotary atomizing heads, a paint is supplied to a cylindrical or bell-shaped main body which is put in high speed rotation for atomizing and spraying the paint toward an object to be coated. By way of example, a couple of prior art paint coating machines with a bell type rotary atomizing head (hereinafter referred to as "rotary atomizing head type paint coating machines" for the convenience of explanation) are shown in the drawings.
Shown in FIG. 16 is a first prior art rotary atomizing head 100 which is mounted on a paint coating machine. The rotary atomizing head 100 is largely constituted by a main body 101, and a hub member 102 which is located within the main body 101 and securely fixed to the latter by means of set screws 103. Indicated at 104 is a housing of the paint coating machine, and at 105 is a rotational shaft which supports the atomizing head 100. Through a paint feed tube 106, a paint is supplied to the rotary atomizing head 100 which is supported at the fore end of the rotational shaft 105.
Shown in FIG. 17 is a second prior art rotary atomizing head 200 which is mounted on a paint coating machine. Similarly, this rotary atomizing head 200 is largely constituted by a main body 201 and a hub member 202 which is mounted within the main body 201 and securely fixed to the latter by means of a rear screw portion 203. Denoted at 204 is a housing of the paint coating machine and at 205 is a rotational shaft which supports the atomizing head 200. A paint is supplied to the atomizing head 200 at the fore end of the rotational shaft 205 by way of a paint feed tube 206 which is extended axially through the rotational shaft 205.
In some cases, more particularly, in coating operations using paints of different colors, the rotary atomizing heads of this sort need to be dismantled and disassembled for washing them clean and reassembled each time when changing the paint color.
In this regard, the hub member 102 in the above-described first prior art rotary atomizing head 100 is fixed to the main body 101 by means of set screws 103, while the hub member 202 in the second prior art rotary atomizing head 200 is fixed to the main body 201 by threaded engagement therewith of the screw portion 203. Accordingly, whenever there arises a necessity for washing the rotary atomizing head 100 or 200 clean, the hub member 102 or 202 need to be disassembled from and reassembled with the atomizing head body 101 or 201 by loosening and tightening the set screws 103 or the screw portion 203 before and after washing. However, a problem with the above-described prior art rotary atomizing heads has been that the disassembling and reassembling jobs require a tool for loosening and tightening the screws 103 or the screw portion 203 and usually take a long time.
Besides, in most of rotary atomizing head type paint coating machines which are currently in use, the rotary atomizing head is put in high speed rotation of 20,000 r.p.m. or higher to produce higher atomization effects on the spray of paint particles, so that meticulous skills are required in setting the rotary atomizing head precisely in a rotationally balanced state substantially free of radial run-outs in high speed rotation.
In this regard, in case a hub member 102 and 202 is detachably or separably fixed to a main body 101 and 201 in the above-described prior art, the rotary atomizing head could lose rotational balances depending upon the degree of tightening of a screw or screws in a reassembling process even if the rotary atomizing head 100 and 200 were once set in a rotationally balanced state. Therefore, the rotary atomizing heads as in the above-mentioned prior art constructions 100 and 200 give rise to another problem that a great deal of time and cost has to be spent for checking and readjusting rotational balances.
In this connection, it may be conceivable to maintain initial rotational balances of a rotary atomizing head by inseparably fixing a main body and a hub member to each other by the use of pins or by press-fitting. In such a case, however, it will require toiling efforts to wash off paint deposits which persistently remain in solidified state on various parts of the rotary atomizing head.
In view of the problems inherent to the prior art, it is an object of the present invention to provide a rotary atomizing head assembly which can be easily disassembled, washed and reassembled, and yet which can easily restore rotational balances after reassembling.